In recent years, marketing products in packaging containers such as retort pouch and the like which keep foods as contents are required to avoid alterations of food tastes and of the qualities during a period from the production of products until eating by customers. Therefore, packaging materials provided a light blocking property by a lamination of films with metal foils such as aluminum or a vapor deposition layer, are used for such packaging materials.
On the other hand, since retort foods and the like provided by the above mentioned packaging containers are widely commonly distributed and consumed, packaging containers made by the above mentioned packaging materials come into circumstances to be disposed as wastes, and in case of a thermal disposal of packaging containers, the fact that metal portions in packaging materials remain as residues in incinerators, is acknowledged as a problem.
From this point of view, in order to acquire a light-blocking property without the use of metals such as aluminum, a colored printed layer formed in layer constructions of packaging materials has become to be tried. While, the forming of a color printed layer has big advantages to reduce production costs because it can be easily conducted by printings during productions of packaging materials, in case that a color printed layer is formed by an all-over printing with black color which has a great effect for acquirement of a light-blocking, it is not applicable for food packaging materials in appearance, and in case that an all-over printing in white color provides drawbacks of insufficiency for light-blocking property.